Field of the Invention
The invention relates to a concave adjustment mechanism in threshing apparatus of a combine harvester, and in particular to threshing apparatus that can accept different concave grate segments for harvesting different crops.
Description of Related Art
Agricultural combines are large machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The clean grain can then be transported from the grain tank to a truck, grain cart or other receiving bin by an unloading auger. In a rotary processing system the crop travels axially parallel to and helically around the rotational axis of one or more rotary processing devices commonly referred to as rotors. In conventional, or tangential-flow, systems, during at least a portion of its travel through the system the crop travels in a transverse or tangential direction relative to the rotational axis of a rotary processing device. In each case, grain is processed between elements affixed to the periphery of the rotary device and arcuate, usually foraminous, stationary processing members in the form of threshing concaves or separating grates that partially wrap around the lower portion of the device.
The radial clearance between the threshing elements and the grates is typically adjustable to cater for the harvesting of different crops. Moreover, it is well known to provide interchangeable sets of grate segments which are suited to different crops, the grate segments being supported by a concave frame which is adjustable with respect to the rotor.
For example, a concave grate suited for small grains may include a fine matrix of square bar elements, whereas a concave grate more suited for corn may include a wider matrix of rounded bar elements. Different crops often require different concave clearances. By way of example, corn is typically harvested with a greater concave clearance than when harvesting wheat. The interchangeable grate segments are thus typically manufactured with an optimum radius so as to be concentric with the rotor at their typical operating setting. As a result a corn concave grate segment typically has a larger radius than a small grain concave segment.
When the concave segments are installed in the concave frame, the radial clearance must be adjusted accordingly to suit the harvesting conditions faced. When the larger radius corn concave segments are fitted to the concave frame however, special care must be exercised to ensure that the clearance adjustment is kept at a setting which is sufficient to avoid the grate segment interfering with the swept envelope of the rotor and causing damage.